Myanmar and IRRI design solar rice dryer

The solar bubble dryer is being tested in Cambodia, Myanmar, the Philippines, Vietnam and Africa. (Image source: IRRI)

Myanmar’s department of agriculture, along with partner NGOs and IRRI, have designed and set up a solar dryer to protect rice grains from sudden rain, pests and intense heat

Named solar bubble dryer, it was designed by a team of experts from the University of Hohenheim, GrainPro. Inc., and IRRI.

According to Ana Salvatierra, researcher at the University of Hohenheim, the name comes from the unique characteristics in its design: ‘Solar’ due to ambient conditions that provide heat from the air that flows inside the dryer and ‘bubble’ for the dome-like shape of the cover or roof when it is set up.

“In the early designs, we included a chimney, but it was not very efficient to move air through the drying tunnel. And when there was a typhoon, the chimney fell. So, we reworked the design using small ventilators to move air. That’s when we also came up with the bubble concept,” she added.

The small ventilator inflates the bubble and circulates air. The airflow then removes water from inside the drying tunnel, where the grains are, and prevents overheating. To make sure that the grains dry evenly, they are stirred from time to time using a metal roller underneath the dryer.

“Based on our grain quality results in the lab, its drying performance is quite satisfactory,” Salvatierra said.

It can dry rice grains to a moisture content level of 10 per cent to 13 per cent, depending on whether the weather is dry or wet.

“The dryer is still a work-in-progress, but it has numerous advantages over a mechanical dryer for small farmers. It is affordable, easy to use, and is ideal for rural areas without a power grid or source of electricity,” said Martin Gummert, head of the IRRI post-harvest unit.

“Unlike most dryers that require higher amounts of paddy to dry, the solar bubble dryer has a capacity of one tonne, which it can dry in one to two days, depending if it’s sunny or rainy,” he added.

A typical recirculating batch dryer, for example, requires at least 10 tons of rice in just one drying operation. Because it needs electricity to run the dryer and fuel for the air heater at the same time, the investment and operating cost for such a dryer is higher.

Gummert said, “An additional benefit of the solar bubble dryer comes from its photovoltaic solar panels that provide power to the battery of the ventilators.”

“In Myanmar, many farming villages do not have access to electricity. The solar panels and the battery can also be used for other purposes, such as lighting the house when the dryer is not used,” he explained.

Currently, the solar bubble dryer is being tested in Cambodia, Myanmar, the Philippines, Vietnam, and Africa.